1. Field of the Invention
The present invention relates to a method of manufacturing a heat exchange tube for use with a heat exchanger employed in an automobile air conditioning system, such as a condenser, an evaporator, a heater core, or a radiator.
The present application is based on Japanese Patent Applications No. Hei. 10-239175 and 10-331443, which are incorporated herein by reference.
2. Description of the Related Art
Light metal material having good heat conductivity, such as aluminum or an aluminum alloy, is used as the material of a heat exchange tube for use in a heate exchanger, such as a condenser of an automobile air conditioning system. Particularly, there is employed a clad material comprising a base material and a brazing layer which is formed on the surface of the base material, from a metal of the same family as the base material. A tube base material is formed so as to assume a closed cross section by connecting together two sheets of tube raw material, each of which is formed from the clad material. The tube base material is heated in a heating furnace such that junctions on the circumferential surface of the tube base material; i.e., the mating faces of the sheets of tube raw material, are brazed, to thereby constitute a tube. In order to ensure brazing of tube raw material, powder flux is sprayed onto and electrostatically adheres to the side surface of the respective mating faces of the sheets of tube raw material. Alternatively, a flux solution is sprayed onto tube raw material such that flux adheres to the side surface.
Spraying of powder flux or a flux solution onto the tube raw material results in wasteful adhesion of flux to areas other than the area to be brazed and disadvantageously adds to cost. Further, splashing of flux deteriorates the working environment and stains surrounding facilities.
Accordingly, the object of the present invention is to provide a heat exchange tube manufacturing method which prevents waste of flux, deterioration of the working environment, and staining of surrounding facilities, which would otherwise be caused by splashing of flux, and which advantageously enables manufacture of a heat exchange tube by coating a tube with tube raw material on tube forming lines.
According to the present invention, there is provided a method of manufacturing a heat exchange tube. In the method, a metal plate is bent in multiple stages to thereby constitute a tube base having a closed cross section, only portions of the metal plate to be brazed is coated with slime-like flux between two of the multiple stages of the bending step, and the tube base is heated so as to braze the portions to be brazed, to thereby manufacture the heat exchange tube.
Further, an inner fin is inserted into the metal plate from an opening thereof during the bending step and after the coating step.
According to the present invention, in a process of forming a tube base of a heat exchange tube, flux is applied to solely the portions of a metal plate to be brazed, and flux is not applied to the other portions of the metal plate that do not require brazing, thus preventing waste of flux. Further, the flux is applied in the forming process on a line for forming a tube base, thereby eliminating provision of a flux coating process on another line. Accordingly, facilities required for manufacturing a heat exchange tube can be reduced, thus achieving cost cutting advantageous for manufacture.
Further, since slime-like flux is used, there can be prevented deterioration of the working environment and staining of surrounding facilities, which would otherwise be caused by splashing of flux.
In the step of forming a tube base, a corrugated inner fin is inserted into the metal plate that has been bent so as to assume a substantially U-shaped cross section, from an opening of the metal plate, thereby facilitating insertion of the inner fin. Further, the slime-like flux applied to the portions of the substantially U-shaped metal plate to be brazed is prevented from being scraped off at the time of insertion of the inner fin. Accordingly, in addition to the above-described advantageous results, the present invention yields the advantage of enabling the inner fin and the tube base to be brazed without fail.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.